Studies were initiated to look for expression of sis oncogene in primate embryos and normal term placenta. Preliminary studies have failed to demonstrate expression of the sis oncogene during embryogenesis, but sis has been demonstrated to be expressed in most placentas which have thus far been studied using v-sis and c-sis probes hybridized to poly-A RNA extracts of the placentas. Another line of study is an examination of an epidermal growth factor (EGF)-dependent mouse keratinocyte line. Studies are underway to see whether oncogenes are expressed when the cells are stimulated with EGF following a period of EGF privation. Another effort has been to try to adopt RNA in situ hybridization to the cell-specific study of oncogene expression. This has thus far been unsuccessful, probably due to low copy number. However, the method has been successful in demonstrating viral infection of cultured cells.